Breathing mask



FIG. 1 is a front and side perspective view of a breathing mask showing my new design;

FIG. 2 is a side elevational view thereof;

FIG. 3 is a top plan view thereof;

FIG. 4 is a front elevational view thereof; and,

FIG. 5 is a rear elevational view thereof. 

The ornamental design for a breathing mask, as shown and described. 